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150 Cards in this Set
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- 3rd side (hint)
Geology
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science pursuing an understanding of Earth
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Physical Geology
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examines materials composing Earth to understand processes that operate beneath and on its surface
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Aspects of geology affecting people
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(1)Natural Hazards
[flood, earthquake, volcano, landslides] (2)Natural Resources [oil & gas, metals, coal/uranium, gravel/sand, H20] |
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Geologic time scale
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-Billions of years
-reoccurance normally longer than human life span -100 million yrs ago = recent -rock sample 10 million yrs old = young |
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Science assumes...
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the natural world is consistent and predictable
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Goal of science...
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discover patterns in nature to make predictions from
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Science collects facts through..
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observation & measurement
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The Earth system is powered by
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(1) The Sun
---drives external processes [climate, erosion] (2)Earth's interior. -a-heat remaining from its formation -b-heat still generated by radioactive decay (powers the interal processes that make volcanos/earthquakes/mountains) -Earth convects like a boiling pot exchanging heat from inside to surface |
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plate tectonics are driven by
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convection of the mantle
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Greater size of planet = slower loss of heat
[relating to earth/mars?] |
Earth is still shedding heat
Mars = smaller = already lost internal heat =never convected = no plate techtonics = 1 LARGE volcano rather than multiple small volcanos |
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3 main rock types
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IGNEOUS
SEDIMENTARY METAMORPHIC |
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The Rock Cycle shows:
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the cycles in which rocks change into other rocks
shows processes that materials change on the surface & inside of earth |
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Nebular Hypothesis
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bodies in solar system evolved from enourmous rotating cloud [the solar nebula] made of gasses and dust grains
--solar nebula slowly contracted due to gravity ---rotated faster ---cload assumed disk shape w/concentration @ center (the pre-sun) ---gravitational energy converted to thermal energy [sun formed] ---cooling of cloud caused rocky material to condense into solid particles ---collisions caused particles to grow into planets |
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Earth is ___ yrs old
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4.5 billion
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Geologic time scale made by:
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first fossils
then given actual numbers using radioactive dating |
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Origin of Earth
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1. big bang
(larg explosion sending all matter of universe flying outward at high speed) 2. debris (mostly H and He) colled/condensed into first stars/galaxies ---in our galaxy=milky way=our solar system formed 3. Nebular Hypothesis *earth & other planets formed from same material as sun 4. Layered structure of earth developed 5. dense material moves to center of earth... light material stays at shallow levels |
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Earth's Layers
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-iron rich core
-the mantle (largest layer) -thin primitive crust |
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Formation of Earth's core
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-intense heating due to radioactive decay
-causes iron and nickel to melt -dense liquid metal sank toward center of planet |
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Formation of Earth's Mantle
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-same early heating formed buoyant masses of molten rock
-light molten rock rose toward surface -solidified to form primitive crust *enriched in O2 |
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Earth's internal layers can be defined by:
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1) chemical composition
2) physical properties |
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Earth's Layers Defined by Chemical Composition:
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1)Crust
2)Mantle 3)Core |
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Earth's Layers Defined by Physical Properties
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1) Lithosphere (crust & uppermost mantle)
[acts like brittle solid] 2) Astehnosphere [acts like plastic solid] 3) Mesosphere (lower mantle) 4) Core (outer & Inner) |
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Chemical Comp. of Crust
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1)oceanic crust
-composed of igneous rock (BASALT) 2)continental crust -many rock types (upper=mostly granitic, lower=mostly basalt) |
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Chemical Comp. of Mantle
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-82% of earth's volume
-uppermost mantle=mostly peridotite (@ greater depth peridotite has more compact crystalline structure & greater density) |
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Chemical Comp. of Core
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-iron nickel alloy (mix)
-minor amts of O2, silicon, & sulfur (form compounds easily w/ iron) |
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Physical Prop. of Lithosphere
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-consists of crust and uppermost mantle
-cool rigid shell (cool=strong=rigid) |
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Physical Prop. of Asthenosphere
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-in upper mantle
-soft, comparatively weak to lithosphere -has a small amt of melting -mechanically detached from lithosphere = *the lithosphere can move independently of asthenosphere* -acts like plastic solid |
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Physical Prop. of Lower Mantle (mesosphere)
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-increased pressure counteracts high temps
=rocks gradually strengthen with depth -rigid strong, but still hot and capable of gradual flow |
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Physical Prop. of Core
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1)outer core
- liquid layer - convective flow of metallic iron =generates magnetic field 2)inner core -high temps but stronger than outer core due to immense pressure -behaves like a solid |
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Moon
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Made up of same rocks as Earth
About the same age as Earth |
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Formation of Moon
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-impact of mars-size planet w/early earth
-ejected debris entered orbit around earth -condensed to form moon *ejecterd material mostly iron-poor mantle & crustal rocks == small iron core on moon |
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Terrestrial v Jovian planets
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Terrestrial:
-small -inner planets -Mercury Venus Earth Mars -rocky -minor ice -minor gas == meager atmospheres Jovian: -Large -Outer planets -Jupiter, Saturn, Uranus, Neptune -gases (hydrogen, helium) =thick atmospheres -ices (water, amonia, methane) |
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Escape Velocity
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the speed a gas molecule can evaporate from a planet
-bigger planets = higher escape velocities = difficult for gas to evaporate from them -moon unable to hold gases = lack of atmosphere ====no weatering/erosion |
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Earth has less craters than moon
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bc of Earth's greater atmosphere
friction [in earth's atmosphere] burns up small debris before it hits the ground |
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ejecta
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ejected material from crater when meteoroid strikes
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Earth v. Mars
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both terrestrial planets
Mars: -smaller -atmosphere is 1/100 density of earth's atmosphere -polar caps = water ice covered by frozen carbon dioxide -lost heat early in history ====mantle never convected ====no plate tectonics ====all heat lost through one place ====gigantic volcano [ex. mons olympus] -lost magnetic field and atmosphere ====less erosion |
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Reasons for Mars' giant volcanos
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-lost heat early in history
[no plate tectonics=heat lost in one place] -smaller than earth [less gravity=longer til gravity pulls down volcanos] |
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Where do we land on mars?
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@ low elevations so atmosphere = thicker
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Jarosite
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found on earth and on mars
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Meridiani landing site on mars
[possible life?] |
Bedrock is exposed in shallow craters, suggesting that this part of Mars is covered by only a very thin layer of windblown deposits -and it may be relatively easy to observe and analyze underlying rocks.
Rock outcrops or soil may contain insitu hematite -helping to explain its origin Evidence for hematite in volcanic or hot-spring deposits may be a great place to look for evidence of past life (e.g. fossils). |
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Mineral
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IT MUST
1) Occurs naturally 2) Inorganic Solid 3) Possess orderly internal structure [atoms must be arranged in a definite pattern] 4) Definite Chemical Composition |
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Rock
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Solid aggregate (minerals joined so properties of each are maintained) mass of minerals
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Mineral's ordered internal structure means...
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every sample of the same mineral contains the same elements joined together in a pattern
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Elements atomic structure:
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nucleus contains protons = # of nuetrons
electrons surround nucleous -located in shells (energy levels) |
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Atomic # determined by
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# of protons
-atoms w/same atomic # = same element |
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Element
definition |
collection of electrically neutral atoms with the same atomic number
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Valence Electrons
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Outermost electrons
-the ones involved in chemical bonding |
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Chemical Bonding
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formation of a compound by combining 2+ elements
1.Ionic* 2.Covalent* *usually occur together 3.Metallic |
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Ionic Bonding
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gain/loose valence electrons to form ions
-after electron transfer, atoms no longer electrically neutral -*aka* the attraction of oppositely charged ions to one another making a neutral compound [Ions=atoms with an electrical charge -anion (- atom) -cation (+ atom)] [ionic compounds=arrangement of oppositely charged ions *internal atomic arrangement of minerals determined by size of ions] |
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Covalent Bonding
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-atoms share electrons to gain neutrality
-covalent compounds stronger than ionic compounds |
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Metallic Bonding
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Valence electrons free to migrate among atoms
-weaker & less common than covalent/ionic |
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mass #
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Nuetrons + Protons
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Isotope
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atom with variation in mass #
-same # protons -varying # nuetrons **can have unstable nuclei that emit particles/energy = RADIOACTIVE DECAY [clock for earth's history] |
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Polymorph
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Minerals with same chemical compositions but different cystalline structures
*2 minerals with same chemical comp can be joined together in different ways ==2 minerals w/different properties can have the same chemical comp. -ex. diamond & graphite {both polymorphs of carbon} =both consist of carbon =difference = how they were formed [diamonds=compact, formed at greater depth graphite=widely spaced, weakly held together] *heating graphite under high pressure can make diamonds *peanut butter in high pressure can make diamonds |
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The ordered atoms in a mineral form a particular crystalline structure.
The internal atomic arrangement is determined by: |
-charges of the ions
-size of the ions involved |
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Physical properties of minerals
(list) |
1) Crystal Form
2) Luster 3) Color 4) Streak 5) Hardness 6) Cleavage 7) Fracture 8) Specific Gravity 9) Other |
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CRYSTAL FORM
physical property |
External expression of ordered internal arrangement of atoms
-crystal growth can be interrupted by not enough space or rapid heat loss *not cleavage |
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LUSTER
physical property |
appearance of mineral in reflected light
-1-metallic (have appearance of metal, regardless of color) -2-non-metallic -other: oily, silky, earthy |
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COLOR
physical property |
unreliable
highly variable for a given mineral due to slight variance in chemistry |
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STREAK
physical property |
color of mineral in powdered form
-helpful in determining different forms of same mineral |
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HARDNESS
physical property |
resistence of mineral to scratching
-determined by rubbing mineral with unknown hardness against one of known hardness -compared on a standard scale: MOHS SCALE OF HARDNESS [10 minerals arranged in relative ranking from 1(softest-talc) to 10(hardest-diamond)] |
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CLEAVAGE
physical property |
tendancy to break along bonds
-produces flat, shiny surfaces -described by resulting shapes (# of planes, & angles joining planes) *no cleavage called fracture |
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FRACTURE
physical property |
absence of cleavage when mineral's broken
*quartz |
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SPECIFIC GRAVITY
physical property |
ratio of weight of mineral to equal volume of water
-avg value = 2.7 -hefting mineral can work too (comparing weight of mineral in hand to common rocks) |
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OTHER
physical properties |
-magnetism
-reaction to hydrochloric acid -malleability -double refraction (transparent mineral over printed material makes words appear twice) -taste -smell -elasticity |
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Conchoidal Fracture
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minerals that break into smooth curved surfaces resembling broken glass
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Rock-Forming Minerals
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common minerals that make up most of Earth's Crust
-8 main elements making up 98% of Crust |
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8 main elements in crust:
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1)Oxygen
2)Silicon 3)Aluminum 4)Iron 5)Calcium 6)Sodium 7)Potassium 8)Magnesium |
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Silicates
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-most important mineral group
-most of rock forming minerals are silicates -abundant bc large amt of silicon & O2 in earth's crust -basic building block = SILICON-OXYGEN TETRAHEDRON molecule ===4 oxygen ions surrounding smaller silicon ion |
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Different Silicate Structures
(how silicon-oxygen tetrahedrons are joined) |
-isolated tetrahedra
-ring structures -single chain structures -double chain structures -sheet structures -layered structures -complex 3D structures |
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OLIVENE
silicate mineral |
-no cleavage--conchoidal fracture
--forms small rounded crystals -Crystalizes @ high temps -Predominantly Iron & Magnesium (Fe-Mg Silicate) ---typical mantle mineral -individual tetrahedra linked by Fe & Mg ions (single tetrahedra structure -black->olive green color -glassy luster |
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PYROXENE GROUP
silicate mineral |
-single chain
-cleavage: 2 planes @ Right Angles -Bonded by Fe & Mg ***AUGITE*** -black, opaque mineral -one of the dominant minerals in Basalt |
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AMPHIBOLE GROUP
silicate mineral |
-double chain
-cleavage: perfect cleavage; 124 & 56 degree angles -Bonded by variety of ions ***HORNBLENDE*** -dark green-->black -similer in appearance to augite (except for cleavage |
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MICA GROUP
silicate mineral |
-sheet structures
-cleavage: sheet structures result in one direction of perfect cleavage (one plane) ***BIOTITE*** -common dark colored mica -shiny, black -iron rich ***MUSCOVITE*** -common light colored Mica |
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FELDSPAR GROUP
silicate mineral |
-3D structure
-cleavage: perfect cleavage: 2 planes at 90 degrees -most common mineral group ***Orthoclase (potassium feldspar)*** -contains potassium -light cream -->salmon color ***Plagioclase (sodium & calcium feldspar) -white->gray color |
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QUARTZ
silicate mineral |
-3D structure
-NO cleavage -consists entirely on silicon & oxygen -light colored (varies) -light weight -**6 sided shape** -develop pyramid shaped ends |
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Clay Minerals
(still silicates) |
clay= general term to describe variety of minerals
-all have sheet structure -originate from chemical weathering |
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important
NON-SILICATE MINERALS |
-oxides
-sulfides -sulfates -native elements -carbonates -halides -phosphates |
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CARBONATES
non-silicate minerals |
primary constituents in limestone & dolostone
***Calcite ***Dolomite |
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Non-silicate minerals
w/ economic value |
-Hematite
(oxide mined for iron ore) -Halite (halide mined for salt) -Sphalerite (sulfide mined for zinc) -Native Copper (native element mined for copper) |
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Igneous Rocks
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form as molten rocks cool/solidify
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Characteristics of Magma (molten rock)
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-parent material of igneous rocks
-forms from partial melting of rocks in earth *called lava only when reaches surface |
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Extrusive / Volcanic Rocks
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rocks formed from lava at surfacee
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Intrusive / Plutonic Rocks
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rocks formed from magma that crystallizes at depth
[ex. Granite] |
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3 Components of Magma
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1)MELT: liquid portion (mobile ions of elements from crust-mostly silicon & oxygen)
2)SOLIDS:(if any)silicate minerals that have already crystallized 3)VOLATILES:gases dissolved in melt [H20, carbon dioxide, sulfur dioxide] |
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Crystallization of Magma
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as magma cools ions in the melt loose their mobility & arrange themselves in an ordered crystalline structures
(normally O2 and silicon link together first |
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Igneous Rocks are Classified by
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1. Texture
(size/shape/arrangement of interlocking crystals) 2. Mineral Composition |
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Factors Contributing to Texture of Igneous Rocks
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1) the rate magma cools
-slow cooling = fewer & Larger crystals -fast rate = many small crystals -very fast rate = glass (no time for ions to arrange=unordered ions=glass) 2) amount of silica present 3) amount of dissolved gases in the magma |
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Types of Igneous Textures
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1)Alphanitic (fine grained)
2)Phaneritic (coarse grained) 3)Porphyritic 4)Glassy 5)Pyroclastic (fragmental) 6)Pegmatitic |
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APHANITIC
igneous texture |
-fine grained texture
-rapid rate of cooling of lava or magma -microscopic crystals -can contain Vesicles [holes from gas bubbles] |
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PHANERITIC
igneous texture |
-coarse grained texture
-slow cooling -crystals identified w/o microscope -ex GRANITE |
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POPHYRITIC
igneous texture |
-minerals form at different temperatures & different rates
-Large crystals [PHENOCRYSTS] are embedded in a matrix of smaller crystals [GROUNDMASS] |
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GLASSY
igneouos texture |
-very rapid cooling of igneous rock
-OBSIDEAN=resulting rock (arrowheads) |
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PYROCLASTIC
igneous texture |
-various fragments ejected during violent volcanic eruption
-superheated/superfast flows -appear similar to sedimentary rocks |
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PEGMATITIC
igneous texture |
-exceptionally coarse grained
-forms in late stages of crystallization of granitic magmas -VERY Large crystals |
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Dark (ferromagnesian*) Silicate Minerals that Igneous Rocks are Composed Of
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-olivene
-pyroxene -amphibole -biotite mica *ferromagnesian=contain Fe or Mg in structure & are heavier |
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Light Silicate Minerals that Igneous Rocks are Composed of
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-Quartz
-Muscovite Mica -Feldspars *not much Fe & Mg |
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Granitic v Basaltic Composition of Igneous Rocks
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1)Granitic:
-light colored silicates -"felsic" (feldspar & silica in composition) -high amounts of silica -major part of earth's crust 2)Basaltic -composed of dark silicates & feldspar -"mafic" (magnesium & ferrum {iron} in composition) -more dense than granitic -make up ocean floor & many volcanic islands |
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GRANITE
igneous rock |
-Granitic (felsic)
-phaneritic -65% quartz -25% feldspar -abundant -associated with mountiain building -"granite" covers many different mineral compositions -pink & coarse-grained |
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RHYOLITE
igneous rock |
-GRANITIC (Felsic)
-extrusive equivalent to granite [granite that made it to the surface] -alphanitic texture -less common than granite -phenocrysts (large crystal embedded in matrix can be quartz or feldspar) |
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BASALT
igneous rock |
-BASALTIC (mafic)
-volcanic origin -alphanitic texture -composed mainly of pyroxene & plagioclase feldspar -most common extrusive igneous rock |
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GABBRO
igneous rock |
-BASALTIC (mafic)
-intrusive equivalent to basalt -phaneritic texture of pyroxene & plagioclase -makes up a lot of oceanic crust |
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OTHER COMPOSITIONAL GROUPS OF IGNEOUS ROCKS
(other than granitic & basaltic) |
1) Intermediate (Andesitic) Composition
-25+% dark silicate minerals -associated with explosive volcanic activity 2)ULTRAMAFIC Composition -rare -high in Fe & Mg -composed entirely of ferromagnesium silicates |
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ANDESITE
igneous rock |
-INTERMEDIATE (andesitic) composition
-volcanic origin -alphanitic texture -resembles rhyolite |
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DIORITE
igneous rock |
-plutonic (deep magma origin) equivalent to andesite
-coarse grained -intrusive -made up of intermediate feldspar & amphibole |
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Silica Content Changes Magma's Behavior
GRANITIC V BASALTIC MAGMA |
1)Granitic Magma
-high silica content== ==more viscous (=thicker)== ==usually lose mobility before reaching surface ==tend to produce large plutonic structures (rocky mtn nat'l park, pikes peak) -still liquid at low temps (700 C) -goes BOOM when erupts -[Yellowstone] 2)BASALTIC MAGMA -low silica content -fluid-like behavior -crystallizes at high temps -Gurgles when it erupts -[Hawaii] |
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OBSIDIAN
igneous rock |
-GRANITIC (felsic)
-dark colored -glassy texture -usually when lava's put out quickly |
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PUMICE
igneous rock |
-GRANTIC (felsic)
-volcanic -glassy texture -frothy appearance (extrusive foam) -usually found with obsidian -formed when large amts of gas escape through lava (generates gray frothy mass) -many samples float in water |
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PYROCLASTIC ROCKS
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composed of fragments ejected during volcanic eruption
-2 types of pyroclastic rock: 1)Tuff -ash sized fragments 2)Volcanic Breccia -particles larger than ash |
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Geothermal Gradiant
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Change in Temperature with Depth
-rate of temp change avgs at 20-30 C per Kilometer |
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Origin of Magma
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originates by rocks melting in earth's mantle
-since mantle is made of mostly solid rock, magma is formed when rocks are raised above their melting point. -rocks are raised above their melting point by: 1)added heat 2)decrease in pressure 3)introduction of volatiles |
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Heat's role with Magma
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-rocks in lower crust/upper mantle are near melting points
-rocks lowering into mantle or heat rising from mantle helps induce melting |
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Pressure's role with Magma
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-melting occurs at higher temperature due to pressure
-when pressure drops enough "Decompression Melting" is triggered ==[rock can ascend into lower pressure areas]===responsible for magma at plate bounderies |
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Volatile's role with Magma
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volatiles (gas components of magma)---USUALLY WATER---
Cause rocks to melt at LOWER temperature -effect of volatiles magnified by increasing pressure -volatiles play important role where cool slabs of oceanic crust lower into mantle |
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Melting & Crystallization of Magma temperature range
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Both span a great temperature range of about 200 C
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Processes Responsible for Different Magma Compositions
(and thus wide variety of igneous rocks) |
1)Magmatic Differentiation
2)Assimilation 3)Magma Mixing 4)Partial Melting |
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MAGMATIC DIFFERENTIATION
{changing magma composition} |
**WHEN 2+ SECONDARY MAGMAS FORM FROM A SINGLE PARENT MAGMA**
because minerals crystallize at different temps a seperation of solid and liquid in magma can occur -this happens when earlier formed crystals are denser than the liquid magma -the solid crystals sink to the bottom of magma chamber -when the remaining melt solidifies it will have a much different chemical composition from the first solid crystals & the parent magma |
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ASSIMILATION
{changing magma composition} |
**CHANGING A MAGMA'S COMPOSITION BY THE INCORPORATION OF FOREIGN MATTER (surrounding rock bodies) INTO A MAGMA**
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MAGMA MIXING
{changing magma composition} |
**TWO BODIES OF MAGMA INTRUDING ONE ANOTHER**
-2 chemically distinct magmas can produce a composition much different from the either original magma |
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PARTIAL MELTING
{changing magma composition} |
**INCOMPLETE MELTING OF ROCK**
since the melting of rocks has such a great temp range minerals with lowest melting temps are first to melt. -as melting continues magma approaches the composition of the rock it was derived from -most of the time complete melting, however, does not occur |
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Formation of Basaltic Magmas
From Partial Melting |
-most originate from partial melting of ultramafic rock in mantle
-form at: (1)mid-ocean ridges by decompression melting (2)subduction zones (water driven from descending slab of oceananic crust promotes partial melting -as basaltic magma migrates up pressure decreases & reduces melting temperature (magma doesn't crystallize @ depth) -outpourings are common on earth's surface |
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Formation of Andesitic Magmas
From Partial Melting |
-interactions between basaltic magma & silica-rich parts of earth's crust generate andesitic magma
(ex. basaltic magma migrates up & melts/assimilates crustal rocks it ascends through) -Can also form from magmatic differentiation (as basaltic magma solidifies the silica-poor minerals crystallize first. =the remaining melt (now enriched in silica) has an Andesitic Composition [secondary magma] |
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Formation of Granitic Magmas
From Partial Melting |
-likely to form as the end product of the crystallization of andesitic magma (magmatic differentiation)
-or partial melting of silica rich continental rocks |
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Factors that determine violence/explosiveness of Volcanic Eruption
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The viscosity determines the violence which is determined by:
1)Composition of Magma 2)Temperature of Magma 3)Dissolved Gasses in Magma More Visous = More Explosive |
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Viscosity
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measure of material's resistence to flow
[higher viscosity->difficult to flow] Factors Affecting Viscosity 1)TEMPERATURE: higher temp = less viscous = more fluid (like syrup) 2)COMPOSITION: -higher silica = more viscous (ryolite) *more silica means impeded flow bc silica's in chain structures -lower silica = lower viscosity [more fluid] (eg mafic lava{basalt}) 3)DISSOLVED GASSES: -volatiles (dissolved gas in magma) increase the fluidity of magma (lower viscosity) -gases expand as magma nears earth's surface due to decreasing pressure -violence of eruption depends on how easily gases escape from magma |
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How do Dissolved Gasses affect an eruption
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-volatiles (dissolved gas in magma) increase the fluidity of magma
IN addition -more gas= more force to propel lava... -before an eruption volatiles (gaseous component of magma) migrate up and accumulate near top of magma chamber =upper portion of magma is enriched in gases =gas-charged magma moves from chambe and risses through vent =as nears surface pressure is reduced =gases expand =dissolved gasses release suddenly (like pop can) *fluid basaltic magmas allow gasses to rise with ease. produce lava fountains. *calm eruptions* *more viscous magmas = much more explosive. prior to eruption magmatic differentiation leaves iron-rich minerals behind & upper portion of magma is enriched in silica & dissolved gasses. when magma in upper portion is released, pressure drops on magma below and explosion is followed by emission of degassed lavas. *ryolite or andesite* *yellowstone & mt st helens go BOOM* ------dissolved gasses=1-6% of magma----mostly H20 & Carbon Dioxide |
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Types of Basaltic Lava Flows
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1) Pahoehoe Flows
-smooth skin that wrinkles as still molten subsurface continues moving -twisted ropey texture -(can make lava tubes) -hotter, richer in gasses, faster than aa flows 2)Aa Flows -rough jagged blocky texture -pahoehoe can turn into Aa |
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Pyroclastic Material
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propelled blobs of lava ejected from volcano ("fire fragments")
Types: 1)Ash & Dust -fine glassy fragments 2)Pumice -pourous rock from "frothy" lavas 3)Lapilli -walnut sized 4)Cinders -pea sized *Particles Larger than Lapilli* 5)Blocks -Hardened/cooled lava 6)Bombs -ejected as hot lava balls -~10cm long |
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Crater
(volcano terms) |
steep walled depression at the summit
-less than 1 km in diameter -smaller than a caldera |
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Caldera
(volcano terms) |
very large circular depression at summit
-larger than 1 km in diameter -its a collapse structure -produced by a collapse that followed a massive eruption |
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Vent
(volcano terms) |
the opening of a pipe that connnects to a magma chamber
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3 Types of Volcanos
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1) Shield Volcanos
2) Cinder Cones 3) Composite Cones |
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Shield Volcanos
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-broad, dome-shaped
-made up of Basaltic Lava -covers large area -produced by mild eruptions of mass amts of lava -ex. Mauna Loa (hawaii) -Olympus Mons (on mars = huge shield volcano -calderas common to mature shield volcanos -once a shield eruption volcano is well established most of lava flows through lava tubes -> increase the distance lava can travel before it solidifies |
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Cinder Cone
Volcanos |
-Built from ejected lava fragments (mainly cinder-sized)===>>made of pyroclastic material
-steep slope -have large deep craters -usually product of single eruptive episode -usually small -usually occur in groups |
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Composite Cone
Volcanos (Stratovolcano) |
-potentially dangerous
-most located in "ring of fire" which rims the PACIFIC OCEAN -large, classic shape (thousands feet high, miles-wide base) -due to thick lava that travel short distances -made up of interlayed layers of lava flows and layers of pyroclastic debris -most violent volcanos -often produce nueé ardente [the most destructive form of pyroclastic flow] -Can produce a LAHAR [a volcanic mudflow] -ex. Mt St Helens |
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nueé ardente
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-the most destructive pyroclastic flow {flows of a mix of hot gases, ash, & large rock fragments}
-the bottom portion is suspended by jets of buoyant gases passing up through flow -trapped air provides buoyancy ===travels in nearly frictionless enviro =====can race down steep volcanic slopes ==go up to 200km/hr **produced by composite cone volcanos** |
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Lahar
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a mudflow occuring when volcanic debris becomes saturated with water
-can be triggered by ice melting when volcano erupts **caused by composite cone volcanos** |
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pyroclastic flows
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explosive mix of rock glass & heat
-only with felsic & intermediate magma -ash, pumice & other fragments propelled at high speed |
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Crater Lake formed from a Caldera
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the magma chamber is partially emptied
-the dome part of volcano collapses -forms crater :) |
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The greatest volume of lava is extruded by:
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FISSURE ERUPTIONS
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fissure eruptions
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basaltic lava is extruded from fractures in crust (called FISSURES)
-some can flow far away from source (*flood basalts*) & cover huge areas -occur worldwide -ex. Columbia Pateau ----Snake River Plain in |
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Lava Domes
(volcanic landform) |
bulbous mass of solid lava
-from explosive eruptions of gas rich magma (silica rich) [late stages andesitic composite cones... looks like bulge inside of top of volcano] |
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Volcanic
Pipes v Necks |
PIPES:
-short channels connecting magma chamber to surface NECKS: -resistent vents left standing after erosion has removed volcano (ex devils tower in wyoming) |
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Dikes
Sills Lacolliths are all |
intrusive igneous features
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Intrusive or Extrusive Igneous features?
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Dikes
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-a crack that cross cuts rocks
-sheetlike injection -occurs when magma's injected into fractures -look like a wall if material around it erodes -"injection into a fracture" -**vertical** |
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Sills
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-formed when magma's injected sideways into rock layers
-only form at shallow depths where pressure from rocks on top is low (so they can be lifted so sill can flow inbetween) -"injection into a bedding plane" -**horizontal** |
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Lacollith
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-occur when magma's intruded between layers near the surface
-magma generating lacollith more viscous (less fluid) & collects, pushing overhead rocks upward -lens/mushroom shaped mass -"arches overhead strata upward" -similar to sill |
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Granite is Usually Found in
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Continents
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Oceans or Continents?
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Basalt Usually found in
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BOTH oceanic and continental settings
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Oceans or Continents?
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Most Volcanos are Located
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Within / Near Ocean basins
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